Modern Gasworks Practice

CONTROL OF HORIZONTAL RETORT SETTINGS 137 that time, sufficient gas may be admitted to restere it by means of a 2-inch by-pass at the inlet Valve to the washers. On restarting the work, all that is necessary is, after a few retorts have been charged, to open the washer valve and close the safety seal at the condensers. By this rnethod. all risk of explosion in hydraulic mains, of which many of ns have probably had experience, is entirely obviated, perfect safety is secured, and very little good gas is lost.” It is interesting to note that previous to the above remarks, Mr. Tysoe had said that “ Sunday stoppage means a loss, however it is carried out ” ; which recalls the faet that at that time (twenty years ago) heavy charges had not been thought of. Now, of course, given a good coal, there is not the least necessity for any loss whatever. Controlling the Heats As retort charging is discontinued during the stopping period, it is quite unneces-sary to keep the furnaces up to their full working pitch. The last charges put into each retort are allowed to “ stew ” during tlie whole twelve or eighteen hours, hence a considerable amoumt of heat may be dispensed with and fuel economized. Ideas differ somewhat considerably as to the most effeetive way of adjusting the producers, but the best and most economical results are, no doubt, obtained by merely using the main-flue damper to make the adjustment (this being closed down to about 75 per cent, of the normal amount); whilst, if preferred, the primary- and secondary-air slides may also be closed down by about half. The slides and dampers may then be opened again to their full working extent about 3 p.m., so as to be in readiness for the fresh coal charges at 6 p.m. If the dampers, etc., are regulated in this way, the furnaces should easily outlast the whole period without requiring further charging with fuel. In faet, the latter is one of the features to aim at, in order to dispense entirely with retort-liouse labour. The Value of Water-Gas Perhaps one of the most serious objections to the usual Sunday stop is the possibility of sudden demands arising from such unlooked-for causes as fogs. However short the cessation of gasmaking may have been, it is always followed by some inroads into the gas available, and somewhat depleted Stocks are the result. In some cases a works might conceivably find itself in an unenviable position should an abnormal demand, arise after the retort-liouse hånds had been dismissed for the day. It is under such circumstances that the value of a water-gas plant is felt; and, furthermore, should the quality of the coal-gas have suffered from that evolved during the stop, a little further carburation will soon put matters right. Here the question of diffusion, and the value of the holders in this respect, plays some part. It may generally be taken for granted that should any inferior gas go forward to the holder, it will thoroughly intermix with betaer quality gas therein, with the result that the average quality is quite up to the normal. At times, however, there would appear to be some doubt as to whether complete diffusion does actually take place, and in holders in which the inlet and outlet pipe are side by side it seems possible that the gas (or certainly some portion of it) travels direct from one pipe to the other